Process for polymerization of diolefins



May 15, 1945. w. A. scHuLzE ET Al.

PROCESS FOR POLYMERIZATION OF DIOLEFINS Filed Jah. 24, 1942 lNvEN-ron WALTER AScHu/ zz A WILLIAM/v. AXE

BY l

r1-on Y .Patented May 15, 1945 vPitocizss 'Fon PoLYMnaIzA'rIoN oF DroLEFINs Walter A. Schulze and `William N. Axe, Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation 'of Delaware' Application January 24, 1,942, serial Nt. l423,123 12 claims. (ci. 26o-93) The present invention relates to a new process for the production Aof polymers of high molecular weight from butadiene and like aliphatic conjugated ldioleilns. More particularly it relates to the preparation of plastic, oily and rubber-like synthetic products through the catalytic polyfA merization of butadiene or the like.

This' invention has as one object the provision of a new and improved process for the manufacture of polymers of aliphatic conjugated dioleins such as butadiene. A further object is the disclosure .of reaction conditions including temperature, pressure and concentration of polymerizable dioleiin which result in theproduction of useful polymers. Still another object is to provide an improved manipulative procedure for'carrylng4 out the polymerization. Numerous other objects will appear from the following description taken in conjunction with the accompanying drawing which portrays diagrammatically, with the reaction chamber in section, one form4 of apparatus Y which has been found particularly suitable for.

carrying out the process of the present invention in a continuous manner.

We have discovered that the polymerization of dioleiins of the butadiene type can be accomplished at moderate temperatures and pressures in the presence of selected organic complex or addition compounds of boron iluoride and aliphatic acids. The nature of the' catalyst and the about one-half to about 1 mol` of boron iluoride with one mol of acid. 'I 'he liquid .addition compounds formed are stable, at moderate temperatures and under the conditionsof the present process..-

v In accordance with the present invention, an aliphatic conjugated diolei-ln -of the .butadiene type (i. e. butadiene or its homologues such as for example isoprene, piperylenes, 2, S-dimethylbuta-- diene, etc, or substitution products of butadiene .or its homologues), and'preferably butadiene itself, is polymerized by means of a polymerization catalyst consisting of a liquid addition compound of boron iluoride and an valiphatic saturated unsubstituted monocarboxylic, i;e. a fatty, acid of from 1 to 5 carbon atoms, at a temperature ranging from about r F. to about 120 F., and preferably from about 30 F.' to about 100 F., at sub-L stantially atmospheric pressure, and in the pres ence of a large'volume of an inert diluent.4 vThe diluent is preferably a solvent for both the diole-A iin and for at least the lower liquid polymers thereof, and is preferably immis'cible with the. catalyst. l r

" Immiscibilityof the diluent o 'solvent with the liquid catalyst is advantageous vcause it permits ready separation, after reaction, of catalyst from diluent or solvent containing polymer, the separation talc'ing place. either in a separating zone products together with the general procedure for carrying out the polymerization reactions resultv in a process for the production of dioleiin .polymers, which is substantially different any process` heretofore described.

A The polymerization catalysts used in accordL ance with this invention comprise thel liquid complex compounds formed in reactions of boron fluoride with aliphatic monocarboxylicjacids.

With simple acids of this class, containing from 1M to 5 or more carbon atoms, two series of addition compounds are probably formed during the reaction with boron iuoride. These compounds vare tentatively classied by the' following tyne"for Amulas, although other formulas may exist:

BF; -R-COOH and BF; (Rf-COOH):

in which R is hydrogen or an alkyl group; .Although essentially pure compounds'oi' each `series can apparently be prepared, in` actual practice the liquid acids when saturated with boroniluo, ride appear to take up from 0.5 to 1 mol of boron fluorideper mol of acid. Accordingly .the liquid catalyst used in accordance with the present in- .apart from the reaction zone-or in the said reaction zone itself. This separation may 'conveniently' be effected by allowing layer formation' under the influence of gravity or by centrifuging the liquid catalyst being the heavier. 'Ihe advantage of this ease oi separation due to immiscibility outweighs the advantage of possibly more intimate contact which would be Obtained were the diluent a mutual solvent for both the catalyst andthe diolen. Suiliciently intimate contact for'rapid polymerization may be readily and economically obtained byagitating vigorously the two immiscible phases in any suitablemanner as. for *example by stirring, by passing-through a centrifugal mixing pump, or other contacting device.

Another important. feature o'f our invention is that the concentration of unreacted butadiene'or y oth'er diolen, throughout the reaction zone and Period is maintained at a low iigure;.namely below about 10 volume percent of the solution phaseand preferably below about 2 volume percent down tosay abouti volume per cent, or even lower. This maybe effected by using a sufilcient volume of inert diluent or solvent, and/or vention is formed by the combination of fromll by introducingl the fresh `butadiene into the rel terial designed to give intimate contact.

rently and are very intimately contacted. One' of these liquids consists of the liquid catalyst and the other consistsl 'of 'the inert diluent or.

solvent in which is dissolved 'the butadiene or the soluble polymers thereof and in which is suspended any insoluble polymer. The reaction zone-is preferably sufficiently long, andi there is preferably suiliciently intimate and extended contact therein, that the solvent or diluent issuing therefrom contains substantially no unreacted butadiene but onLv the dissolved and/or suspended polymers thereof. I'n addition 'conditions are maintained such that the concentration of unreacted butadiene at no point in the reaction zone attains thelimits set forth above. In

practice, if the concentration of butadiene is` kept below these limits at the `beginning of the reaction zone, it will necessarily be below these limits inthe rest of the reaction zone.

Preferably the oppositely travelling immiscible liquids are vigorously agitated throughout the tial operating conditions in the manner disclosed herein will automatically determine correct relative proportions. However it may be stated that major portion of the reaction zone for intimate f contact andrapid reaction. Settling. zones, in

` .which there is little or no agitation and there-l fore quiescent opportunityforlayer separation, may be provided at both ends of the reaction zone.` Under some circumstances the reaction zone may be packed with suitable packing ma- Preferably the reaction zone takes the form in batch operation the amount of inert solvent or diluent may be as high as about 50 times by weight that of the catalyst. However more catalyst than this may `be employed.4 In a continuous process the amount of catalyst may range as high as an amount equal .to that of the diluent.

When polymerizing butadienen accordance with-the present invention, we prefer to use atemperature ranging from about 30 to about 120 F. or substantially atmospheric temperature. Temperatures of from about 80 to about 100 F. are infmany cases preferred. As the temperature approaches about 120 F., less desirable polymers are obtained. Above 120 F. and especially above 130 F. the products from butadiene are still less desirable for the purpose at hand.

When polymerizing homologues of butadiene, materially different temperatures, than for butadiene, may be found preferable.

While the invention is generally applied to butadiene, which is normally gaseous, it may be l applied to homologues thereof, which are normally liquid, such as isoprene, piperylenes, 2,3- dimethylbutadiene, 2-chloro-butadiene, etc. In

' such case the diolefinmay be introduced to the reaction zone either' as such, in the liquid or gaseous form, or in the form o'f a previously prepared solution in the solvent or diluent employed.

VThe production of valuable polymers from butadiene or the like is carried out in the preferred embodiment of our invention by bringing together in a suitable liquid paranin hydrocarbon reaction medium and/or diluent, the aliphatic acid-boron fluoride catalyst, and relatively small and closely controlled amounts of butadiene i either as the substantially pure compound' or in of a vertical column equipped with a vertical agitator intermediate its ends and in winch catalyst descends and diluent and diolen ascend' in countercurrent relationship. The catalyst is removed at the bottom and returned to the'top while the solution and/or suspension of is removed at the top. Any suspended may be removed and the solution or turned to the bottom of the column.

librium is soon established at the desired efficient and economical concentration of polymer in the diluent, whereupon a portion of `the solution i8 withdrawn from the polymer solution circuit and treated in any suitable manner to separately re` vcover the polymer and solvent or diluent there-V from. If desired, though less preferably, the entire diluent or solvent, containing the polymer in solution and/or suspension, leaving the top of the reaction column may be treated to recover all rof the polymer therein and the so recovered polymer-free solvent or diluent recycled tothe bottom of the column.

. The dioleiln may beiutroduced directly into' the bottom of the columnat a suitable rate 'in `gaseous or liquid form, preferably the former in v the case of butadiene, or in the form of a solution in either fresh or recycled solvent. Such a solution may be formed just prior to its point -of entry into the bottom of the column. A

While it is diilcult to fix precise limits for the relative proportions of catalyst, diluent, diolen and polymer in the reaction zone, the discussion herein will enable thoseskilled in the art to readily practice the invention without such explicit limits, since the fixing of the other`essen.

vthe catalyst and diluent.

the polymerization proceeds to maintain optilmum concentratie o and the polymer products are eventually separated by suitable means from The preferred solvents and/or diluents for the process are the low-boiling paramn hydrocarbons,I preferably those which are normally liquid having from four to eight atoms br even more, such as pentanes, hexanes and the' like; which are substantially inert under the polymerizing conditions aud which are easily separable from the catalyst yand the -products of polymerization. These hydrocarbons may be used Aas the pure compounds or as more or less closely fractionated cuts from natural gasoline, or other available paraiiinic hydrocarbon mixtures. Pentane is preferred. Y

In the operation of our process we have found that it is exceedingly important that the concentration of butadiene or other diolen in the polymerization zone be maintained at a low level in order to facilitate control ofthe reaction conditions and the nature of the resultant products.` Thus, we prefer to maintain the volume cratio of butadiene to hydrocarbon diluent or solvent below 1:10 at all times, and best results/are often obtained with butadiene concentrations in the polymerization zone not exceeding 1 to 2 volume per cent o'f the solvent or diluent phase.

Polymerization of butadiene with the catalyst the hydrocarbon solvent and/or y pressures are ordinarily unnecessary when they solvent or diluent is properlyy chosen and polymerization temperatures are closely controlled.

-We have noted that under the above-described reaction conditions the action of our aliphatic monocarboxylic acid-boron fluoride catalyst is entirely diflerent from that observed for boron fluoride alone. Our preferred catalysts. are not only much more active in promoting the polymerization of diolens of the butadiene type under these conditions, but also produce polymers of different and much more desirable characteristics.

Examples of suitable aliphatic saturated monocarboxylic acids which may be used are: i'ormic, acetic, propionic, butyric, and valerio. In generalacetic acid is preferred. Higher fatty acids which form, with boron fluoride, addition compounds which are solid within the above temperature range are less desirable for liquid phase contacting although they may be employed in certain instances* in suspension in the reaction mixture.

Referring to the accompanying drawing, I represents a storage. tank containing a liquid hydrocarbon mixture containing a major proportion of mrtg-diene from which said mixture is withdrawn in" gaseous form via line 3 andn passed into the bottom of reaction chamber 6. A suitable hydrocarbon solvent and/or' diluent is stored in tank 2 from which it is pumped by pump 5 through line 4v into reaction chamber 6. The reaction chamber B is operated with the liquid level maintained at the height of withdrawal to line 0. During containing the polymerized butadiene is removed j continuously via line 8 and recycled by means of line 9 and pump 5. After apredetermined viscosity of the polymer solution and/or suspension has been attained,`the productv is partially diverted via line IIIA into a separator IIIB while the a suitable cooling uid circulated through cooling jacket I9. A vent line 23 is provided with an automatic pressure release valve 22 in order to maintain substantially atmospheric pressure. within the polymerization zone.

Where batch operation is employed, a preferred method of contacting involves the suspension of the liquid catalyst in the diluent in a Heat of polymerization is removed by means oi'.l 'y' I finely divided state, as by vigorous agitation.

Butadiene, ordinarily in ,the gaseous state, is introduced beneath the liquid surface at such rate that it all reacts in the reaction zone and that at no point therein are the above limits of unreacted diolefin concentration-exceeded and while maintaining reactionconditions such 'that' the butadiene is intimately dispersed i'n finely divided form immediately upon its introduction. This gradual addition is continued until a product of the desired characteristics has been produced. The addition of butadiene is so regulated that substantially complete reaction thereof takes place. Temperature control may be by means of internal cooling coils. Batch operation may be advantageous where polymers of very high molecular weight are to be formed. Such' 'polymers are not soluble in the preferred aliphatic parafn hydrocarbon diluent and/or remaindersis recycled'with added make-up solvent added from 2. Entrained catalyst is separated by gravity in IIIB and returned to the' catalyst recycle pump I3 via line 20. The supernatant layer of polymer solution passes from sep-- arating zone IIlB via line NC to. zone I4 where condenser 2l where they 4are condensed to'liquid form, and thence to solvent storage 2. The finished polymer is withdrawn through line Il. iluoride-acetic acid additionvcompoundin 250cc.

solvent.

The amount of the catalyst employed will depend on the total volume of the hydrocarbon polymerization medium and the eiciency of the means for suspending or dispersing the catalyst throughout the hydrocarbon liquid. It is desirable to have complete and uniform dispersion Commercial butadiene of 94 `per cent purity waspassed into a suspension of 2 cc. of boron fluoride-acetic acid addition compound in 250 cc. of n-pentane with mechanical agitation. flow `rate of gaseous butadiene was maintained at ce. per minute and the .reaction temperature was controlled between 48 and 55 F. 'Substantially complete reaction of lbutadiene took placel during the'active life of the catalyst to produce 70 g. of pentane-insoluble polymer and 10 g. of pentane-soluble product. Entrained The .of catalyst in more or less nely divided form .Y

catalyst was removed from the insoluble polymer with dilute sodium hydroxide to give a non.

v-"I'l'xe pentane-soluble portion ofthe reaction product was recovered as a clear, colorless, viscous oil by washing the original vpentane'solution with dilute alkali and subsequently removing the solvent by distillation.

Example 2 Commercial butadiene of 94 per cent purity was passed into a suspension of 2 cc. of boron The product consisted of approximately 50 g. of pentane-insoluble and g. of pentane-soluble polymer. Example 1. The insoluble polymer was apale yellow, soft, resilient material which was insoluble in non-aromatic hydrocar-bonabut which Asoftened and swelled in aromatic hydrocarbons.

The pentane-soluble portion was recovered as a clear viscous oil.

Example 3 A ca/talyst was prepared by saturating technical butyric acid with boron iiuoride While maintaining the reaction temperature between 80-100 F. Approximately 0.7 mol of boron uoride was absorbed per mol of acid.

Commercial butadiene of at least 90 per cent purity'was passed into a suspension of 5 cc. of

the boron Afluoride-butyric acid catalyst in 250 cc. of n-pentane during mechanical agitation. The butadieneiow rate was maintained at 85 cc. per minute and the temperature oi reaction was held at l5-85 F. At the conclusion of the reaction l3 gsof pentane-soluble and 45 g. of insoluble polymeric material was recovered in the manner previously described. I'he insoluble polymer was a tough, dough-like mass, while the soluble polymer was a colorless viscous oil.

The choice of the inert hydrocarbon .diluent will vary with the boiling point of the diolen The products were recovered as inA in the reaction zone at, less than about 2 volume per cent -of the diluent phase throughout the reaction. i g 3.-l A process for the polymerization of an aliphatic conjugated diolefin which comprises contacting said diolen withan addition compound oi' boron fluoride and an aliphatic monocarboxylic acid in the presence o f a large volume of an inert diluent which` is selectedfrom the group consistlng of paraln hydrocarbons of from four .to eight carbon atoms. f

4. A process for the polymerization lof butadiene which comprises contacting same with an addition compound of boron fluoride and an aliphatic monocarboxylic acid in thepresence of a large volume o f an inert diluent 'which is pentane.

5. The process ofpolymerizing an aliphatic conjugated diolenh which comprises establishing being polymerized and the nature of the polymers.

Therefore all diluents described are not equally satisfactory for 'eachdioleiin It will be understood that the various aliphatic conjugated doleflns are by no means equivalents in all aspects of the present invention. Experience in synthetic rubber production has emphasized the diierences in a reaction zone oppositely flowing intimately contacting streams of a liquid addition compound centration of unreacted dioleiin in the 'reaction zone at less than 10 volume per cent of the diluent phase throughout the reaction. I

6. 'Ihe continuous process of Apolyme'rizing an l aliphatic conjugated dioleiin which comprises establishing two endless iiowing Vcircuits of a liq- 'uid addition compound of Iborpniluoride and an aliphatic monocarboxylic acid on the one hand and a. solution of said diolen in a parain hydro'carbon as'an inert solvent on the other hand, said circuits overlapping to form a polymeriza-v tion zone in which the ow is countercurrengand in which said compound is descending ands'in solution ascending, continuously introducing unreacted diolen to the bottom of said zone, .con-

tinuously withdrawing a' portion of the solvent stream issuing from the top of said zone, and recovering polymer therefrom.

7. The process of polymerizing butadiene which product of boron iluoride and an aliphatic monocarboxylic acid downwardly in said column, vigorously agitating the material in said column h to promote intimate contact and rapid reaction,

It is to he understood that theinvehtion is not limited to the specific examples lwhich have been offered merely as illustrations' and that the modiiications may be made Within the scope of the appended claims without departing from the spirit of the invention.

We claim: l. A process for the polymerization of'a'n aliphaticconjugated diolefln which comprises conl tacting said diolen with an addition compound of boron fluoride and an aliphatic monocarboxylic acid in the presence of a large volume of a paraffln hydrocarbon as an inert diluent, and maintaining the concentration of unreacted d'ioleiin in the reaction zone at less than about 10 volumeper cent of the diluent phase throughout the reaction.

-2. A process for the polymerization of an aliphatic conjugated dioleiln which comprises contacting said dioletln with an addition compound of boron fluoride and an aliphatic monocarboxyllc acid in the presence of a large volume of a parafiln'hydrocarbon as an inert diluent, and' maini taining the concentratlon'of unreacted separating` catalyst at the bottom of said column and recycling to the top thereof, withdrawing solvent phase from the top of said column and recycling a portion of said solvent phase to the bottom of said column, introducing fresh unreacted butadiene to the bottom of said column,'in troducing solvent to the bottom of, said column, withdrawing the balance of said 'withdrawn solvent phase from the system at a, rate equivalent to that at which said fresh butadiene is'introduced, 'recovering butadiene polymer from said balance of said. solvent phase, maintaining the' temperature in said column betweenabout 30 F.

.and about F. `and the pressure at substantially atmospheric, and maintaining the concentration of unreacted butadiene throughout the reaction zone at below about 104volume per cent of y 120 F. at substantially atmospheric pressure, and

maintaining the butadiene concentration below about 10 volume per cent of the hydrocarbon diluent phase.

9. A process for the simultaneous production of hydrocarbon soluble and insoluble polymers from butadiene which comprises contacting butadiene in the presence of sutiicient paraiiinic hydrocarbon diluent to produce butadiene concentrations 'not substantially exceeding two volume per cent, at temperatures in the range of from about 45 to about 85 F. with a catalyst consisting of a liquid additioncompound of boron iluoride and an aliphatic monocarboxylic acid of one to ve carbon atoms.

10Q A process for the polymerization of butadiene which comprises contacting same at a temperature of from 80 to 100 F. and atvsub- .boron fluoride 'per mol of acid in the presence of a large volume of a paraiiin hydrocarbon diluent, and maintaining the concentration of unreacted butadiene in the reaction zone at less than 10 iiuoride and an aliphatic monocarboxylic acid in a paraiiinic hydrocarbon liquid as an' inert diluent, maintaining said suspension at temperatures in the range of about 30 to about 120 F., and so controlling the rate of addition of butadiene so that the concentration of unreacted the reaction whereby substantially complete poly- 

